In the working stroke of piston 1 to the right, compressed air is admitted through channels a, d and b to the left end of the cylinder. From the right end of the cylinder, air is forced out through ports f to the atmosphere. Near the end of the working stroke, ports f are closed by the piston and the remaining air is compressed and passes through channel g. This shifts plate valve 2 to the left. At the end of its stroke to the right, piston 1 strikes hammer head 3. In the return stroke, air passes through channels a, e and g to the right end of the cylinder. At the end of the return stroke, compressed air in the left end of the cylinder shifts valve 2 to its initial position.
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